The proposed research seeks to understand how sexually dimorphic aspects of forebrain structure control sexually dimorphic aspects of psychosexual and reproductive function in a carnivore, the ferret. The central hypothesis to be tested is that the processing of volatile odors, arising from sexually active conspecifics, by neurons located in different segments of the main olfactory projection to the hypothalamus, differs in males and in females. Studies are proposed to compare the effects of olfactory bulb deafferentation on sexual partner preference in male and female ferrets and to determine whether exposure to male odors augments the capacity of vaginal-cervical stimulation to activate mediobasal hypothalamic LHRH neurons in females. Additional studies will determine whether prenatal inhibition of estradiol biosynthesis in the male ferret brain results in a female-like pattern of sexual partner preference in adulthood while attenuating the differentiation of a sexually dimorphic cluster of galanin neurons in the dorsal preoptic area/anterior hypothalamus (POA/AH). Other studies will assess the effects of infusing galanin or a galanin antagonist or of excitotoxic lesioning of the dorsomedial POA/AH on ferrets' odor and sexual partner preferences. The effects of these treatments on odor-induced expression of the immediate-early gene, c-fos, in neurons located at different stages of the main olfactory projection to the hypothalamus will also be compared in males and females. Finally, the density of projections from the medial amygdala to several hypothalamic regions will be compared in the two sexes using combined immunocytochemistry for the retrograde tracer, cholera toxin B, and Fos protein. Understanding how the male and female nervous systems process reproductive odors differently in a higher mammal like the ferret could provide new insights into sexually dimorphic brain-behavior relationships in man.